Electricity Full Set

What is an electric field?

A region where a charged object experiences a force.

What determines the direction of an electric field?

The direction a positive test charge would move.

How are electric fields represented?

By field lines; closer lines indicate stronger fields.

What is the formula for electric field strength?

E = F/q, where F is force and q is charge.

What does the spacing of electric field lines indicate?

The strength of the electric field; closer lines mean a stronger field.

How do the electric fields of positive and negative charges differ?

Positive charges have outward field lines; negative charges have inward field lines.

What is a uniform electric field?

A field with equally spaced parallel lines, indicating constant strength and direction.

How is a uniform electric field created?

By placing two parallel plates with opposite charges close together.

What happens to a charged particle in an electric field?

It experiences a force that accelerates it.

How is potential difference related to electric fields?

It is the work done per unit charge to move a charge between two points.

What is the relationship between electric field strength and potential difference?

E=V/d, where V is potential difference and d is distance between plates.

How does the strength of the electric field change with distance from the charge?

It decreases as distance increases, following an inverse square law.

Why is a Van de Graaff generator used to demonstrate electric fields?

It builds up high static charges, creating visible electric field effects.

How can electric fields cause sparking?

High field strength ionizes air particles, allowing current to flow.

What is the significance of electric field strength in safety design?

Prevents breakdown and sparking in electrical equipment.

What causes static electricity?

The transfer of electrons between materials, leading to a charge imbalance.

How do materials become positively charged?

They lose electrons.

What happens when two objects with like charges are brought close?

They repel each other.

What happens when two objects with opposite charges are brought close?

They attract each other.

How is static electricity discharged?

By grounding the object, allowing electrons to flow and neutralize the charge.

What is a practical application of static electricity?

Photocopiers and electrostatic precipitators.

Why can static electricity be dangerous in fuel tanks?

Sparks from static discharge can ignite flammable vapors.

How can static build-up be prevented?

By using grounding or anti-static materials.

What is the difference between conductors and insulators in static electricity?

Conductors allow charge to flow, while insulators hold charge.

What is an electric spark?

A sudden flow of electrons through the air, caused by a large potential difference.

Why does rubbing a balloon on hair create static electricity?

Electrons transfer from the hair to the balloon, charging it negatively.

What is an electric field?

A region around a charged object where other charges experience a force.

How do charged objects affect neutral objects?

They induce an opposite charge on the surface, leading to attraction.

Why do charged objects lose their charge in humid conditions?

Water molecules in the air conduct charge away.

How does static electricity cause shocks?

When touching a charged object, electrons flow to or from your body, creating a sudden sensation.

What is the National Grid?

It is the network of cables and transformers that distribute electricity across the country.

Why is high voltage used in power transmission?

High voltage reduces current, minimizing energy loss as heat.

What is the function of a step-up transformer?

It increases the voltage, reducing current and transmission losses.

What is the function of a step-down transformer?

It decreases voltage to safe levels for consumer use.

Why are power stations typically located away from cities?

To reduce pollution and noise in populated areas.

What type of current is used in the National Grid?

Alternating current (AC).

What are the main sources of energy for the National Grid?

Fossil fuels, nuclear, renewable sources (e.g., wind, solar, hydroelectric).

How do transmission cables minimize resistance?

By using thick wires and low-resistance materials like copper or aluminum.

What safety precautions are necessary for high-voltage cables?

Insulation, high placement, and secure routing to prevent accidents.

How does demand affect electricity supply?

The grid adjusts generation to meet peak and low demand.

What are the environmental impacts of the National Grid?

Land use, habitat disruption, and carbon emissions (depending on energy source).

Why is the National Grid more efficient than local generation?

It allows centralized production and optimized distribution.

How does the National Grid ensure a stable supply?

By balancing supply and demand and using energy storage.

What is the role of backup power stations?

They provide additional energy during peak demand or outages.

Why is renewable energy increasingly integrated into the National Grid?

To reduce carbon emissions and reliance on fossil fuels.

What is meant by the term "power dissipation"?

It refers to the energy lost as heat in an electrical circuit.

Why is power dissipation higher in high-resistance components?

P=I²R, so higher resistance increases the energy lost as heat.

How can transmission losses in power cables be minimized?

By using high voltage and low current to reduce I²R losses.

What is the advantage of using a transformer in power transmission?

Transformers step up voltage, reducing current and minimizing power loss.

How is energy transferred in a circuit?

Energy is transferred from the power supply to the components, often converting into heat, light, or motion.

What is the role of circuit breakers in high-power circuits?

They prevent damage by interrupting excessive currents.

How does power relate to energy efficiency?

Efficient devices convert a higher proportion of input power into useful energy, reducing waste.

How does resistance heating work in devices like toasters?

Electric current passes through high-resistance wires, converting electrical energy into heat.

What happens to power if voltage doubles in a circuit?

Power increases by four times if resistance remains constant (P=V²/R).

What are the implications of high-power consumption for energy bills?

Higher consumption leads to higher energy costs.

Why are low-resistance materials used in power lines?

They reduce energy lost as heat, improving efficiency.

How is power measured in a circuit?

Using a wattmeter or by calculating P=IV

Why does high power output require efficient cooling in circuits?

Excess heat can damage components or reduce efficiency.

How do fuses protect against power surges?

They melt when power exceeds safe levels, breaking the circuit.

What is the significance of a power factor in electrical systems?

It measures how effectively electrical power is converted into useful work. A low power factor indicates wasted energy.

What is the formula for electrical power?

P=IV, where P is power (watts), I is current (amperes), and V is voltage (volts).

How can power be calculated using resistance?

P=I²R, where R is resistance.

What does the power rating of an appliance indicate?

It shows the maximum energy transferred per second when the appliance operates at its highest setting.

How do you calculate energy transferred by an appliance?

E=Pt, where EE is energy (joules), PP is power (watts), and tt is time (seconds).

Why do high-power appliances use more electricity?

They transfer more energy per second, leading to higher energy consumption.

What is the unit of electrical energy commonly used in homes?

Kilowatt-hour (kWh).

How is the cost of electricity calculated?

Cost=Energy used (kWh)×Cost per kWh.

Why do appliances with higher efficiency save energy?

They waste less energy as heat or sound, transferring more to useful forms.

What is an example of a high-power appliance?

Electric heaters, kettles, or ovens.

How can the efficiency of an electrical appliance be calculated?

Efficiency=Useful power output/Total power input ​×100%.

What is the relationship between power, voltage, and current?

Power increases when either voltage or current increases.

How does using low-resistance wires affect power loss?

It reduces power loss as heat, making the system more efficient.

Why is it important to match appliances to appropriate fuses?

To prevent overheating or fire due to excessive current.

How do you calculate current if the power and voltage are known?

I=P/V

What is the difference between rated power and actual power usage?

Rated power is the maximum power an appliance can use, while actual power depends on how the appliance is operated.

What is the frequency and voltage of mains electricity in the UK?

50 Hz and 230 V.

What is the difference between alternating current (AC) and direct current (DC)?

AC changes direction periodically, while DC flows in one direction only.

Why is AC used in mains electricity?

AC is more efficient for transmitting power over long distances.

What are the three wires in a UK plug, and their functions?

Live wire (brown) carries current to the appliance, neutral wire (blue) completes the circuit, and earth wire (green/yellow) prevents electric shocks.

What is the potential difference of the live wire relative to the earth?

230 V.

What is the role of a fuse in a plug?

The fuse melts if the current is too high, breaking the circuit and preventing damage.

Why is the earth wire important?

It provides a path for current to flow safely to the ground if a fault occurs.

What is the purpose of a circuit breaker?

It automatically switches off the current in case of a fault, providing faster and reusable protection than fuses.

What is double insulation, and why is it used?

Double insulation ensures no metal parts are exposed, removing the need for an earth wire.

What is the danger of touching the live wire?

It can cause an electric shock due to the high voltage relative to the earth.

How does the length of a cable affect safety?

Longer cables can overheat and increase resistance.

Why is copper commonly used in household wiring?

Copper has low resistance and high conductivity.

What does a residual current device (RCD) do?

It cuts off the power supply when it detects a difference between live and neutral currents.

Why is the neutral wire at 0 V?

It is connected to the earth at the power station to complete the circuit safely.

How do plugs ensure safety during disconnection?

The design ensures the live pin disconnects last, preventing live circuits from being exposed.

What is resistance, and how is it measured?

Resistance is a measure of how much a component opposes the flow of current. It is measured in ohms (Ω) using a multimeter or calculated using Ohm’s law.

What is the formula for resistance?

R=V/I where V is voltage (volts) and I is current (amperes).

How does the length of a wire affect its resistance?

Resistance increases with the length of the wire because electrons encounter more collisions over a longer distance.

How does the cross-sectional area of a wire affect its resistance?

Resistance decreases as the cross-sectional area increases, as there is more space for electrons to flow.

What is the purpose of a variable resistor in a circuit?

A variable resistor allows control over the current by changing the resistance.

Why is it important to use the same material when comparing wire resistance?

Different materials have varying resistivities, which affects resistance.

What is resistivity, and how does it relate to resistance?

Resistivity is a material property that indicates how strongly it resists current. R=ρL/A where ρ is resistivity, L is length, and A is cross-sectional area.

How does temperature affect resistance in most materials?

Resistance typically increases with temperature due to more frequent collisions between electrons and atoms.

What is Ohm’s law?

Ohm’s law states that V=IR, meaning the voltage across a conductor is directly proportional to the current through it, provided the temperature remains constant.